Tools for use in percussive machines

ABSTRACT

A percussion tool, typically known as a &#39;&#39;&#39;&#39;steel,&#39;&#39;&#39;&#39; having a longitudinally extending stem, a shank portion at one end and a working head at the other end, wherein the stem is sufficiently weighted, at about the mid-point of its length, to inhibit transverse vibration of the tool.

United States Patent 1 1191 Rabett [4 Dec. 24, 1974 [5 TOOLS FOR USE'IN PERCUSSIVE 931,671 8/1909 -Bank 173/162 x MACHINES 1,362,657 12/1920 Whyte....... 173/162 X 1,477,855 12/1923 Thurston... 175/408 x [75] Inventor: Reginald George Edward Rab 2,997,024 8 1961 McLean; 173 139 Chesterfield, England 3,662,855 5/1972 Adams et a1; 173/139 [73] Assignees: Rohert D. Adams, Litt1e Freys, FOREIGN PATENTS APPLI ATI N Wrmgton; Ian 1 m 166,867 7/1921 Great Britain, 175/414 Chandlersford, Hlms, both Of 895,729 11/1953 Germany 173 139 Eng and 1,119,025 6/1956 France 173/139 1,157,386 5/1958 Frzrnce...; 175/320 1 1 111 7 77,382 3/1930"SWCC1CII 173 139 [211 Appl 105588 332,914 7/1930 Great Britain 173 139 Primary Examiner-Richard B. Wilkinson Fore'gn Apphcatlon Pnomy Data Assistant Examiner-,lohn F. Gonzales Jan. 21, 1970 Great Britain 2957/ Attorney, Age m, qr Firm-Robert R.-Paquin 52 Us. (:1 181/33 A, 181/36 A, 2393196? [57] v ABSTRACT I r 51] 1111. C1. E210 13/00 A P P P tool, typically known as 31 8 [58] Field 61 Search 175/414, 320, 325, 408; longlmdmally exfiendmg Stem a Shank P f 173/131, 128 139, 162;.52/733; 30/168; one end and a workmg head at the other end, wherem- /41; 299/94; 16/116; 181/33 A, 36 A the stemns suffic1ently werghted, at abont the m1dpoint of 1ts length, to 1nh1b1t transverse vlbratlon of [56] References Cited the tool- 1 UNITED STATES PATENTS 2 Claims, 4 Drawing Figures 395,700 1/1889 0161766111.; 414 x- H r l H TOOLS FOR USE IN PERCUSSIVE MACHINES This invention relates to tools for use in'percussive machines and is particularly directed-towards a tool of the kind known in the art as, and hereinafter referredto as, a steel comprising a longitudinally extending stem having a shank at one end'thereof by which the steel is adapted to be secured in a percussive machine and a working head at the other end thereof. The work ing head may comprise a spade, chisel", moil, drill bit or the like. Usually, the steel is forged or otherwise formed from a bar of the material steelwhich is of circular or polygonal shape in transverse cross-section.

, In general, the steel is secured in a percussive machine -for the free end of its shank to be repeatedly impacted by a reciprocating hammer device. Such hammer device is usually (but not necessarily) pneumati cally driven as, for example, in the well known handheld pneumatic road drill. A considerable problem encountered with percussive machines is that during their use to drive a steel, a large amount of noise is emitted, the sound level of which'frequently approaches the threshold of pain'for the human ear. It has hitherto been proposed to reduce the noise level of percussive machines by substantially enclosing ormufiling the machine in a bag of sound absorbing material or with a layer of vibration. absorbing material as, for example, disclosed in British Pat. No. 1,055,048. Attempts have been made, it is believed unsuccessfully, to similarly muffle the steel over the major part of its exposed length, but it will be apparent that such muffling severely restricts the use of the steel'since penetration of the steel to practical depths into concrete or other hard material easily damages the muffling material.

wholly located inthe recess- The rib is preferably peripherally formed around and integral-with the stem, for example during forging of the steel andthe collar is preferably formed of substantially complementary shape to the rib to provide an efficient interference fit therewith. The collar can be formed in two or more provided on the steel at a position between the stem I and shank, or when'the collar is to be secured on a rib. the collar parts can be assembled and secured around the stem, for example when the collar comprises a mass of resilient material, by shrinking or swaging a metallic sleeve around the assembled parts to urge them into engagement with the stem (or the recess or rib provided thereon).

It is believed that the upper sound pressure levels emitted by an impacted steel-are due largely as a result of transverse vibrations setup in the steel and'more particularly that such pressure levels which approach thethreshold of pain result from the primary mode-of It is an object of the present invention: to provide a steel which, when in usejwith a percussive machine,

provides a diminution in the noise emitted by the steel when impacted, thatis to say, provides a reduction in the upper sound pressure level emitted bythe steel in comparison with conventional steels.

According to the presentinvention, there is provided a steel of the kind specified in which the steel'is suffi-' from the region of the steel enclosed by the collar, the

ciently weighted substantially at its mid-length position to inhibit its primary mode of transverse vibration.

Preferably the mid-length position of the steel is located on the stem andsubstantially at said position the stem has secured thereto a collar the mass of which is sufficient to inhibit the primary mode of transverse vibration of the steel. The collar may comprise a mass of resilient material secured to the stem which material may be additionally weighted by having high density, preferably particulate, material (such as lead shot) embedded in it. Alternatively, the collar may comprise a sleeve of high density material such as steel resiliently mounted on the stem.

' tached thereto as, for example, by shrinking or swaging techniques. The stem may be provided with a recess or rib with which the collar engages as an interference fit to inhibit its longitudinal movement on the stem. The

recess is preferably peripherally formed around the stem and the length of the collar may be partly or transverse vibration (or the lower frequency mode of inhibited. In addition, the weighting of the steel at the 1 'mid-part of its length may also, to some extent,.mute

torsional and longitudinal vibration of the steel which moderates high frequency longitudinal vibrations emitted by the steel which it is believed reduces the noise level emittedby the steeL'Further, when a collar is resiliently secured to the stem (or the collar comprises a resilient material secured to the stem) at themid-length part of the steel, the collar may provide a shielding effect to diminish the efficiency of the radiation of noise reason for this being that the collar dissipates energy of vibration of thesteel prior to such vibration reaching the external peripheral surface of the collar.

' As will be appreciated from the aforegoing, the

imately nine pounds was found to be considerably-improved (insofar as its noise emission'during use) by weighting the mid-length part of the steel with a collar weighing approximately 1.0 to 4.0 pounds (454 to 1816 grammes). Conveniently the weighting is in the range of 10 to 40 percent of the weight of the steel.

Two embodiments of the'present invention will now be described, by way of example only, with reference to the accompanying illustrative drawings in which:

FIG. 1 shows a conventional steel having secured thereto .a collar (shown in longitudinal section) located in a peripheral recess of the stem and. of sufficient weight to inhibit the primary mode of transverse vibra* 'tion of the steel;

- the collar applied to the steel .as in FIG. 2.

Where possible throughout the following description, the same parts or members in each of the Figures have been accorded the same reference numerals.

The steel comprises a bar (of the material steel) which is of polygonal or circular shape in transverse section and which is forged to provide a shank 1, a stem 2 and a chisel working head 3. A transversely extending flange 4 is forged at the junction of the stem and shank. In use, the steel is secured in a percussive machine (not shown) by the shank l engaging in a complementary socket of the machine so that the free end of the shank may be impacted by a reciprocating hammer. The steel is generally retained in engagement with the socket by a spring member of the machine engaging over the flange 4 in a known manner.

- The stem 2 has a shallow peripheral recess 5 (conventiently formed during the forging of the steel) which is' located to extend longitudinally in the mid-length part of the steel. Located'around the stem 2 to overlie the recess 5 is a collar 6 comprising an annular block 7 of resilient material (in the present example a molded rubber element) and a rigid sleeve 8 of, for example, steel. the sleeve. 8 is swaged to compress the annular block 7 against the stem 2 and deform it into the recess,

v loaded to increase the weight of the collar 6 as, for example, by embedding lead shot (shown generally at 9) in themolded rubber element or by mixing lead dust 4 with the rubber prior to molding. v

In the embodiment shown in FlGS.'2to 4 the stem 2 has a transverselyextendingperipheral rib 10 which is located at the mid-length position of the steel and is conveniently formed during forging of the steel (in a similar manner to the flange 4). Located around the stem 2 to overlie the rib 10 and adjacent part'lengths of the stem is the collar 6 which comprises a two-part structure of resilient material retained on the stem by a steel sleeve 11. The two-part structure of the sleeve comprises two molded rubber elements 12 and 13 which are identical in shape and are each molded (as shown in FIG. 4) so that the profile of their surface 14 which is to be located adjacent the steel conforms to the profile of the mid-length part of the steel which ineludes the rib. Both elements l2-and 13 are assembled on the stem 2 to encircle the rib 10 (see FIG. 3) and,

being of complementary shape to the rib 10, provide an efficient interference fit therewith toretain the collar from longitudinal movement over the shank. The elements l2 and 13 are conveniently bonded together and thereafter the steel-sleeve 11' is swaged on to the elements to urge them into close contact with the shank.

In a similar manner to the embodiment shown in FIG. 1, the elements 12 and 13 and sleeve 11 sufficiently weight the steel at its mid-length position to inhibit the primary mode of transverse vibration of the steel.

Iclaim: I i

l. A percussion tool assembly comprising:

a longitudinally extending stern,

a shankportion formed integrally'with one end of I said stem, I v a peripheral rib extending radially from said tool between said shank portion and the remainder of said tool, said rib for retainingv the shank portion in a percussion apparatus, a working head at the other endof said stem, and a collar assembly at the mid-point of the length of said tool, between the working head and the peripheral rib, said collar being fixed to said stem and comprising a mass of elastomeric material bound and compressed against the stem by metal sleeve means, said elastomeric material being additionally weighted with a higher density material embedded therein, said collar assembly for substantially inhibiting transverse vibrations of the tool. 2. The assembly of'claim'l wherein said higher density material is of particulate form. 

1. A percussion tool assembly comprising: a longitudinally extending stem, a shank portion formed integrally with one end of said stem, a peripheral rib extending radially from said tool between said shank portion and the remainder of said tool, said rib for retaining the shank portion in a percussion apparatus, a working head at the other end of said stem, and a collar assembly at the mid-point of the length of said tool, between the working head and the peripheral rib, said collar being fixed to said stem and comprising a mass of elastomeric material bound and compressed against the stem by metal sleeve means, said elastomeric material being additionally weighted with a higher density material embedded therein, said collar assembly for substantially inhibiting transverse vibrations of the tool.
 2. The assembly of claim 1 wherein said higher density material is of particulate form. 